The invention relates to a VL constant velocity universal joint for accommodating axial displacements in a propeller shaft of a motor vehicle and for connecting a drive unit to a rear axle gearbox, having at least two articulatably connected shaft portions, a standard plunge usable in a damage-free way, an outer joint part with outer ball tracks, an inner joint part with inner ball tracks, a plurality of torque transmitting balls each guided in outer and inner ball tracks associated with one another, with associated outer ball tracks on the one hand and inner ball tracks on the other hand, forming angles of intersection in respect of the central axis A of the joint, which are of identical size but are set in opposite directions, and having a ball cage which is provided with a plurality of cage windows each accommodating one of the balls and which hold the balls in one plane when the joint is axially displaced or articulated, with the outer joint part having to be connected to an annular flange and the inner joint part to a connecting shaft.
Propeller shafts of this type are used in motor vehicles to transmit torque from a front drive unit to the rear axle. Apart from having to ensure functional safety under normal operating conditions, these structures also have to fulfil certain requirements in the case of a vehicle crash wherein the front part of the vehicle and thus the first part of the propeller shaft is displaced towards the rear axle. To prevent the shaft from kinking towards the vehicle cell and in order not to prevent a greatest possible absorption of energy in the front part of the vehicle through deformation work, by supporting the drive unit at the rear axle, and to avoid any damage to the rear axle, it must be possible to shorten the shafts further beyond the range predetermined by the standard plunge of the VL joint with a minimum of energy being absorbed. The component particularly suitable for accommodating such shortening is the respective axially plungeable constant velocity universal joint in the propeller shaft.
Propeller shafts of this type for motor vehicles are known from DE 42 24 201 C2 wherein it is proposed that at the end of the predetermined standard plunging distance between the outer joint part and the inner joint part, the balls of the cage stop against the annular flange and that the connection between the plug-in shaft and the inner joint part is to be destroyed. Hereafter, the plug-in shaft slides into the annular flange and into the hollow shaft adjoining same. This embodiment presupposes plug-in shafts which, with a reduced diameter, follow the toothed region engaging a correspondingly toothed region in the inner joint part.
DE 43 44 177 C1 describes a similar type of propeller shaft for motor vehicles, which comprises a cage-less joint with axis-parallel ball tracks, which cage-less joint, in operation, is suitable for very small articulation angles only. With this embodiment, the plug-in shaft cannot be slid in beyond the predetermined standard plunging region unless the outer joint part and the adjoining tubular shaft are deformed, thus absorbing a large amount of energy.